Image converter tube



June 17, 1958 Filed Feb. 19, 1948 c. s. szEGl-io ETAL IMAGE CONVERTER TUBE' '2 Sheets-Sheeli'. 1

CONSTANTIN S. SZEGHO WILLIAM REED (Ittomeg June 17, 1958 v c. s. s'zEGHQ ETAL 2,839,699

Y IMAGE CONVERTER TUBE Filed Feb. 19, 1948 2 sheets-sheet 2 FIG. y(

/75 Jfa/fgye Vea/frode f nnentor GONSTANTIN S. SZEGHO B 'l WILLIAM o. REED M Gtforneg United States Patent ice IMAGE CONVERTER TUBEl Constantin S. Szegho and William 0. Reed, Chicago, Ill., assignors to The Rauland Corporation, Chicago, lll., a corporation of Illinois Application February/19,1948, serial No. 9,494

9 claims. (ci. 313-66) This invention relates to new and useful improvements in electronic devices for storing intelligence impressed on a photosensitivey surface.

The object of the invention is to insure visible reproduction of the intelligence at any desired time afterV receipt of this intelligence. y

The object is attained by modulating in-accordance with the intelligence a photoelectric instead of the customary electron beam, and focusing the photoelectron image onto the storage electrode.

In accordance with another feature of the'invention, the fluorescent screen of the device isfcovered on the side of the envelope facing the storage electrode by a thin film of aluminum to stop slowly moving electrons and ions, and to insure maximum light reflection towards the person viewing the screen. l

These and other features of the invention will more clearly appear from the claims and the detailed description of an embodiment.

In the drawings:

Fig. 1 is a diagrammatic side elevation in section of the tube showing circuit connections between elements;

and

Fig. 3 is a cross section on lines l3--3 of Fig.V 2.

An evacuated envelope 1 of glass or other suitable material carries on theV inside of one wall a screen of fluorescent material 2 which is covered with'a film of aluminum 3. This film is thin enough to permit the passage of electrons having a certain velocity but will block slower electrons and ions. Also, thisflm acts as a light reflector insuring maximum visibility when viewing the outside surface of screen 2. It also-provides protection to the fluorescent screen against cesium vapor during processing, which would cause the uorescent screen to lose eiiiciency if this vapor permeates it. To insure more elfective protection, it is advisable to keep the aluminum film during processing at a positive potential of the order of 250 volts, thereby repelling positive cesium ions.

Within the main chamber of the envelope parallel with the screen 2, a storage electrode 18 is mounted comprising an electrode 4 of photosensitive material, e. g. a silvercesium-oxide or other suitableY surface deposited on a metal plate S connected to ground in the control circuit over conductor 6 extending Vthrough nipple 7 which projects from the main chamber of envelope 1. The surface of electrode 4 facing screen 2. is covered with a mosaic of separate insulating particles 8 of quartz, alumina or the like, for the storage of charges. The details of storage electrode 13 are shown in Figs. 2 and 3.

The convex end of a hollow branch 9 of envelope 1 supports an image cathode 1l) having a surface of photoelectric material (e. g. silver-cesium-oxide serving as the source of electrons for the device) carrying a negative potential of 600 volts. Branch 9 is inclined at an angle so that the electron image corresponding to the light image striking the image cathode 10 may be focused on the surface of electrode 18. VElectrodes 11 and 12 perform Fig. 2 is an enlarged fragment of the storage electrode;

2V electrostatic focusing and acceleration of thev electron image from image cathode, 10. Electrode 11 also performs the function of a gating rgrid to cut olf-the electron image when desired.

The intensity of the photoelectric imageJi-s modulated in accordance with 4the intelligence signal received at any f instant and it is focused on the storage electrode 18 by means of the electrodes 11 and `12. Thebeam striking the insulating particles 8 buildsup a positive ornegative charge, depending on whether the secondary emission ratio of these insulating particles is greater orless than unity. Thisratio depends on Ythejvelocity.,pf the arriving electrons. This in turn can be influenced by the accelerating' Voltage on electrodes 11 and 12 e. g. negativepotential of 300 voltson electrode `11 andelectrode 12 at ground potential. f

` The intelligence thus conveyed may be `s tored'lor a.v

long period onthestorage electrode 18.

The means for releasing .the energy (intelligence) from the storage electrode may be ultra-violet or infra-red light passed from a source. 13 into themain chamber` of the envelope through a .ilter'14y which impedesthe passage of ambient visible lightinto envelope I'hephotoelectric layer -4 ofV storage electrode 1S thereupon will emit electrons. By means yof, electrodes 1 5 and 16 to Whichpositive potentials of 6 0O volts and 6,000 volts are respectively applied, the electrons released by 4 willbe accelerated and focused to strike the fluorescent screen Y 2 through the aluminum film 3. Y

The electrons emitted by an elemental photosensitiv area of electrode V4 surrounded by positively charged particles 8 will be concentrated in a corresponding 4region of 2 which will lluores'ce more or less brilliantly depending on the amount of charge on the particles 8. Y

The image originally impressed on imagecathode v10 may thus be seen-when desired on fluorescentscreen 2.

Spurious signals generated vby stray infra-red radiation striking image cathode Y10 Vare eliminated b'yapplying a` suitable negative potential tothe electrode `11 while .the stored intelligence is being read.

It is advisable to make the-.spectral sensitivity of elec-V trode 4 to icut olf at infra-red, e. gQb'y usingan antimony cesium'surface. Then light through' image cathode 10 l reaching electrode 4 hasV no influence. The storage electrode 18 may be cleared of charges by flooding it with electrons from the uniformly illuminatedimage cathode 10 and accelerated to a voltage corresponding to the sign of the charges and enough coulombs to overridethese charges. Another way to erase the charges on the insulating mosaic S is to illuminate uniformly the photosensitive electrode 4 and establish a cloud of kelectrons in the neighborhood of insulating mosaic 8 through proper adjustment of the voltagesof electrodes 15 and 16. These electrons will neutralize positive charges onethe insulating mosaic 8. Y

Improved focusing of the image from the storage electrode 18V may be obtained by the addition of an electro- 2. The storage device according to claim l, and in which the'cathode is applied to a transparent portion of the envelope.

3. The storage device according to claim l, and in whichthe screen is applied to a transparent portion of the y Patentedclune ,17, 1958 e 4. The storage device according to claim 1, and in which the screen and storage electrode are parallel.

5. The storage device according to claim 1, and in which ,the storage electrode has a photosensitive layer provided with a mosaic surface. 1

6. The storage device according to ciainr 1,V arid'inV which the axis of the beam emitted by the cathodek is vat an angle to the surface of the storage electrode;.

7. An electronic storage tube comprising an evacu-` ated envelope enclosing a storage electrode 'having a photosensitive layer, one face of which is covered by metal `and the other face by a mosaic of insulated .particles, a fluorescent screen on a Wall of the envelope, means between the storage electrode and screen for acceleratng the electrons emitted-by'th'estorage electrode and focusing them on the-screen', a `photosensitive cathode on the envelope, means for accelerating the photoelectric beam emitted by the cathode and focusingvr it on `the storage electrode, and a window'iny the venvelope through which the mosaic surface of the storagev electrode may beirradiated'. g

8. An electronic storage tube comprising an evacuated envelope having a chamber enclosing 'a storageelectrode having a photosensitive layer of silver-cesium-oxide' one face of which is covered by a metal plate and the other face by amosaic of insulating particles, auorescent screen on a Wall of the chamber parallel with the storage electrode, a Vthin film of aluminum covering the screen on the face opposing the storage electrode, electrodes be*- tween the storage electrode and screen for accelerating the photoelectrons emitted by the storage electrode and focusing them on the screen, an arm of the envelope opening into the chamber at `an angle to the surface of the storage electrode and having a convex end, a photosentive silver-cesium-oxide cathode coated on the inside of the convex end, an electrode Within the arm for accelerating the photoelectric beam emitted by the cathode and focusing it on the mosaic surface of the storage electrode, a grid in the arm for controlling the intensity of the beam, andk a Window in the chamber through which the mosaic surface of the storage` electrode may be irradiated.

9. An electronic storage tube comprising an evacuated envelope enclosing a storage electrode having elemental ReferencesA Cited in the le of this patent UNITED STATES PATEIWIS 2,146,822 Henroteau Feb. 14, 1939 2321,3173 Rose Aug. 27, 1940 Behneet'ali. May 1, 1945 

